Abrasive disk and method of making the same



1942- F. 0. ALBVEIIQTSON 2,292,261

ABRASIVE DISK AND METHOD OF MAKING THE SAME Filed Feb. 19, 1940 jzadezzzziz". flan/E UsierzaflZierZsma M Jaw $76 g Patented Aug. 4, 1942UNITED STATES anansrvn msx AND METHOD OF MAKING THE SAME Frank OsbcrnAlbertson, Sioux City, Iowa, as-- signor to Albertson 8; Company, Inc.,Sioux City, Iowa, a corporation of Iowa Application February 19, 1940,Serial No. 319,639

4 Claims.

in which the curling of the backing is eliminated l and the disk isadapted to maintain its flat or plane condition throughout its effectivelife.

Another object of the invention is the provision of improved abrasivedisks of the type described,

which are adapted to withstand action of water,

oil, or other solvents usually encountered in sanding or grinding work,and which are adapted to hav a particularly fast and effective cuttingaction.

Another object of the invention i the provision of an improved backingfor abrasive disks of the class described which is adapted to beimpregnated more thoroughly than the backings of the prior art, andwhich is therefore adapted to be used for making flexible, non-curlingabrasive disks,

Another object of the invention is the provision of an improved abrasivedisk which is 50 constructed as to eliminate loading or filling of theinterstices between the abrasive particles, and

which is fast cutting, durable, and capable of long service under themost arduous conditions.

Other objects and advantages of the invention will be apparent from thefollowing description and the accompanying drawing, in which similarcharacters of reference indicate similar parts throughout th severalviews.

Referring to the single sheet of drawings,

Fig. 1 is a plan view of the'working face of the abrasive diskconstructed according to the 40 invention;

Fig. 2 is anal! size fragmentary elevational view of the face of thedisk;

Fig. 3 is a half size fragmentary vreareleva- 5 tional view of the disk;

Fig. 4 is a greatly enlarged fragmentary sectional view, taken on theplane Of the lin 4-4 of Fig. 2, looking in the direction of the arrows.

One of the main difficulties in the manufacture of abrasive disks is theprovision of a suitable backing which can be so impregnated with resinthat the moisture condition of the disk may be stabilized and curling ofthe disk eliminated.

It is very dimcult ona commercial basis to backings of the type that canbe bought upon the open market, and according to th present method ofmanufacture of. abrasive disks, the use of a new type of fiber backingis contemplated.

The fibers utilized in this backing are preferably of sisal. The sisalis first treated or soaked in a suitable resin, or the sisal may besprayed with the resin, which is brought to a suitable liquid conditionby th addition of a volatile solvent.

A relatively thin sheet of indurated fiber or kraft paper, such as, forexample, a sheet of flve-thousandths of an inch thickness, is laid on alayer of the impregnated sisal, and th assembly is placed under ahydraulic press, where a predetermined high pressure is applied at thesame time as the application of a curing temperature. The pressure, forexample, may be approximately 1500 pounds per square inch, and thecuring temperature approximately 266 degrees F., when a phenoliccondensation resin is used with a solvent, such as alcohol.

The layer of indurated fiber or kraft paper provides the resultingbacking with a greater strength and flexibility and a proper surface foradhesion of the binder which holds the abrasive particles. The fiber orkraft paper layer is also adapted to absorb the sprayed binder coat,which impregnates this layer and penetrates to such an extent that thebinder and abrasive particles are securely anchored to the backing in away that could not be accomplished by direct application of the binderto a hard cured resin surface which would not absorb sprayed resin.

The next step in the manufacture of the abrasive disk is the spraying ofbinder in the form of a thick coat of a suitable resin, such as aphenolic condensation resin, thinned with'a suitable solvent, such asalcohol. Thereafter, while the binder coat is in a tacky condition, anexcess of abrasive particles is applied to the front surface of thedisk, which is coated with binder, and the particles are embedded in thebinder. I

- The excess abrasive particles not embedded or adhering to the bindermay then be shaken ofi 'by impact of the edge of the disc by or againstsome instrument or support, and thereafter, while the binder coat isstill uncured, the abrasive surface of the disc is suitably shaped bythe application of pressure dies. These pressure dies are preferablyformed with a plurality of ridges, the ridges being formed in two seriesat right secure adequate impregnation with resin of fiber 55 an es to eah o h r nd f rmi v dicated by the horizontal lines in and the verticallines II in the disk I! of Fig. 1.

These grooves and ridges on the die in the abrasive surface arepreferably substantially rectangular in cross section so that thegrooves ll of Fig. 4 are rectangular in cross section, and the ridges l3in Fig. 4 are likewise rectangular in cross section. The ridges l3 are,however, cut up transversely, as shown in Fig. 2, leaving a plurality ofsubstantially rectangular islands H spaced from each other by thegrooves I and II.

It should be noted that the binder coat and application of abrasiveparticles is sufliciently thick so that there is an abrasive surface atthe base of every groove II, as well as at the face of every island 14,and on the sides of each island. This gives the abrasive disk a veryeffective quick cutting action, due-to the high contact pressure of therelaitvely small island areas; but when the island areas H are worndown, the disk is still adapted to have a long cutting life by virtue ofthe abrasive particles which still project below the initial islandsurface and at the base of the grooves I0.

Referring to Figs. 1 and 3, every disk is preferably provided with acentrally located non-circular aperture I5 for engagement with the arboror threaded securing member which secures the disk to a pad.

The disks are preferably manufactured in circular shape from thebeginning so as to eliminate the wastage of the finished backing, andany waste, except that involved in the cutting of the thin induratedfiber layer or kraft paper layer into disks.

Referring to Fig. 4, 25 indicates the main body layer of sisal, itsfibers extending in random directions, with various curvatures, andbeing thoroughly soaked and impregnated with a suitable resin whichholds the fibers together when subjected to hydraulic pressure and heatcuring.

For the purpose of diagrammatic illustration, in Fig. 4 there is shownan external impregnating or sealing layer of the same resin on the sisalbase, indicated at l6, while I! indicates a similar sealing and adhesivelayer of the same resin between the thin indurated fiber or kraft paperlayer l8 and the sisal. Similarly, l9 indicates a layer of the sameresin external to the sisal, at the edges of the sisal and at the edgesof the indurated fiber or kraft paper I8, so that the body of theabrasive disk or backing is completely sealed with the resin.

As a matter of fact, in the manufacture of the abrasive disks, these arenot layers separately applied, but by reason of the impregnation of thesisal fibers with the resin, it is a fact that there is resin on allsides of all of the sisal fibers and at the edges of the disk, and apart of the resin, which impregnates and covers the sisal fibers,produces the sealing effect which is diagrammatically illustrated at l6,l1 and i9; that is, the impregnated sisal fiber may use its own resinfor effecting a seal of/the fibers in the backing and for adhesivelysecuring the kraft paper layer to the impregnated sisal fiber backing.There is an excess of resin which acts as adhesive to secure the kraftpaper to the sisal fiber backing and to seal the sisal fiber within thebacking, and that is diagrammatically illustrated by the layers whichare clearly shown at Figs. 16, 1'7, and 19 in the drawing, but which donot appear as separate, visible layers in the structure of the-abrasivedisc.

material secured to invention,

As all of the resins employed in the disk are preferably of the samematerial in different conditions of viscosity, the abrasive disk ispractically an integral member of the resin with the thin induratedfiber or kraft paper layer, and the sisal fiber enclosed in the resin togive it the desired strength, flexibility and resilientcharacteristics.

After the surface of the abrasive disk has been suitably shaped, asshown in Figs. 2 and 4, the abrasive surface is then again sprayed witha thin binder or anchoring coat of the same resin of a thinnerconsistency, and the disks are then subjected to a heat curing bypassage through an oven or a drying heated atmosphere, which removes thesolvent and renderes the resin hard and insoluble to water, oil, and theusual solvents to which an abrasive disk may be subjected.

The disk may be subjected to a relatively quick evaporation of thesolvent at, for example, a temperature of degrees F. for a period of,for example, twelve hours, and thereafter to a longer heat curing at asubsequent higher temperature of, for example, 230 degrees F. for tenhours.

During this evaporation of the solvent and the curing, the abrasivedisks are preferably held in a substantially plane condition, so thatthey will be set, cured, and hardened in a plane condition.

Various types of the fibrous material may be employed, but the sisal ispreferred, as its strength is not affected by the application of theresin. As distinguished from sisal, it has been found that ordinarycloth and paper becomes brittle when it is impregnated with resin; andbackings of indurated fiber, which are actually made up of laminations,tend to split at the edge, causing the abrasive disk to weaken at theedge, where most of the work is done.

The specific pressure and heat applied and the period of applicationwill vary for different types of resins, and various types of resins maybe employed, the phenolic condensation resin and solvent mentioned beingmerely exemplary of one type of materials. The resin should be one whichis not affected after curing by heat or moisture, and which is strong,not brittle, and adapted to hold its shape. The resin should be toughand bendable and flexible, and yet relatively still when combined withthe sisal fiber in the form of an abrasive disk.

The sisal fiber acts in the same way as a reinforcing for the resin, andthe resin forms the real body of the backing for the abrasive disk. Suchabrasive disks are adapted to have a long life and to maintain theirplane condition, although they are adapted to bend or flex during theapplication of the disk to the work.

While I have illustrated a preferred embodiment of my invention, manymodifications may be made without departing from the spirit of the and Ido not wish to be limited to the precise details of construction setforth, but desire to avail myself of all changes within the scope of theappended claims.

Having thus described my invention, what I claim as new and desire tosecure by Letters Patent of the United States, is:

1. A backing for abrasive disks comprising a disk of resin reinforcedwith sisal fibers extending in random directions throughout said disk,said disk being cured to resilient flexible condition by the applicationof heat and pressure, and said disk having a facing of absorbent paperthe resin before curing, and

adapted to receive a binder for abrasive particles.

2. The method of making abrasive disks comprising soaking sisal fibersin a resin adapted to be rendered insoluble by the application of heatand pressure, forming a disk of the fibers impregnated with resin,applying an absorbent sheet to one face of the assembly of fiber andresin, curing the resulting disk by application of heat and pressure,spraying the absorbent face with binder resin of similar characteristicsto the resin of the disk, applying an excess of abrasive particles,removing the abrasive particles not secured or embedded in the binder,shaping the semi-plastic mass of abrasive particles and binder on theface of the disk to provide a multiplicity of ridges and grooves, allformed with abrasive surfaces, spraying an anchoring coat on theabrasive surface, and subjecting the abrasive disk to curing by heatwhile holding the disk in plane condition.

3. A backing for abrasive disks comprising a disk of resin reinforcedwith fibers extending in random directions, said disk being cured from asingle felted mass of resin impregnated fibers to resilient flexiblecondition by the application of heat and pressure, said disk having anintegrally formed resin seal on all sides of said fibers and at theedges of said disk.

4.- An abrasive disk comprising a resilient, yet flexible, resin diskreenforced with fibers extending in random directions through the bodyof said disk, said resin being cured to an insoluble condition by theapplication of heat and pressure and abrasive particles applied to theouter face of said layer of paper material, the surface of said abrasivedisk being formed with a multiplicity of grooves and ridges, the ridgesbeing substantially rectangular in outline, and the grooves terminatingin the edge of said disk for the discharge of cuttings from the disk,the bases of said grooves being also covered with abrasive particles forinsuring a long life of the abrasive surface.

FRANK O-SBERN ALBERTSON.

DISCLAIMER 2,292,261.Frank Osbem Albertson, Sioux City, Iowa. ABRABIYEDrsc AND METHOD OF MAKING THE SAME. Patent dated August 4, 1942.Disclaimer filed September 16, 1943, by the assignee, Albertson (f:Company, In'c. Hereby enters this disclaimer to claim 3 in said patent.

[Ofiicial Gazette October 19, 1.948.]

